© ISTOCK.COM/NANOSTOCKKIn 1977, biologist Carl Woese discovered that microbes living in anaerobic conditions and producing methane had a genetic imprint very different from known bacteria species. He and his colleagues eventually suggested that researchers stop referring to such methanogens and related microorganisms as bacteria, classifying them instead as members of a new domain in a tripartite division of the living world, alongside Bacteria and Eukarya.
Woese named this domain Archaea (from the Greek archaio, meaning ancient or original) because the microbes he studied seemed to thrive in extreme conditions akin to those of early Earth. Later on, scientists observed archaea in more-diverse environments, from oceanic water and deep sediments to forest soil and the surface of human skin. Recently, a new archaeal group named after its discoverer, Woesearchaeota, was even detected in human lungs. Although archaea superficially resemble bacteria in terms of size and cellular organization (members of both groups lack nuclei), they are surprisingly similar to eukaryotes at the molecular level. For instance, all archaea replicate their DNA and synthesize proteins using molecular machines like those of eukaryotes. This suggests that Eukarya and Archaea belong to a same “super-domain” ...
